Alkylhydroxyphenylcarboalkoxy-substituted phthalimide

ABSTRACT

COMPOUNDS CONTAINING ONE OR MORE ALKYLHYDROXYPHENYL GROUPS BONDED THROUGH CARBOALKOXY LINKAGES TO A NITROGEN ATOM OF A HETEROCYCLIC NUCLEUS CONTANING AN IMIDODICARBONYL   -CO-NH-CO- GROUP HAVE BEEN PREPARED AND ARE EXTREMELY EFFECTIVE STABILIZERS AGAINST THE DELETERIOUS EFFECTS OF OXYGEN, HEAT AND LIGHT FOR ORGANIC MATERIALS. THE STABILITY OF POLYMERIC COMPOSITIONS SUCH AS A-OLEFIN POLYMERS AND COPOLYMERS, ACETAL POLYMERS, POLYAMIDES, POLYESTERS AND POLYURETHANES IS MARKEDLY INCREASED BY THE ADDITION OF SMALL AMOUNTS OF THE PRESENT COMPOUNDS THERETO. -C(=S)-NH-C(=S)- GROUP OR AN IMIDODITHIOCARBONYL

United States Patent Oflice A 4 Claims ABSTRACT OF THE DISCLOSURE Compounds containing one or more alkylhydroxyphenyl groups bonded through carboalkoxy linkages to a nitrogen atom of a heterocyclic nucleus containing an imidodicarbonyl group or an imidodithiocarbonyl group have been prepared and are extremely effective stabilizers against the deleterious effects of oxygen, heat and light for organic materials. The stability of polymeric compositions such as a-olefin polymers and copolymers, acetal polymers, polyamides, polyesters and polyurethanes is markedly increased by the addition of small amounts of the present compounds thereto.

This is a division of application Ser. No. 32,435, filed Apr. 27, 1970, now US. Pat. No. 3,678,047.

BACKGROUND OF THE INVENTION Esters of nitrogen heterocycles containing the imidod'icarbonyl or imidodithiocarbonyl molecular groupings are known, however, the ester substituents have typically been limited to the more common aliphatic hydrocarbon radicals containing up to about 8 carbon atoms. Arylsubstituted isocyanurates have been prepared but have generally been limited to functionally unsubstituted isocyanurates, that is where the aromatic nuclei contain no substitution. In a copending US. patent application Ser. No. 770,863, aryl isocyanurates wherein the aryl substituent is functionally substituted with a hydroxyl group were prepared. The hydroxyaryl group was bonded to the isocyanurate nucleus by a methylene (CH linkage. It would be desirable to have isocyanurates and structurally related heterocyclic compounds substituted with one or more hydroxyaryl groups wherein the hydroxyaryl groups are bonded to the isocyanurate or other heterocyclic nucleus through an ester-type linkage.

SUMMARY OF THE INVENTION We have now prepared compounds containing one or more alkylhydroxyphenyl groups bonded through carboalkoxy linkages to a nitrogen atom of a heterocyclic nucleus containing imidodicarbonyl or imidodithiocarbonyl molecular groupings in the ring. Preferably the alkylhydroxyphenyl group will contain alkyl substitution and more preferably tertiary alkyl groups containing from 4 to 8 carbon atoms immediately adjacent to the hydroxy group on the benzene ring. The total number of carbon atoms making up the carboalkoxy linkage will be between about 2 and 20. While a wide variety of heterocyclic compounds may serve as the nucleus for the compounds of the present invention, so long as they contain one or more imidodicarbonyl or imidodithiocarbonyl molecular group- 3,810,912 Patented May 14, 1974 ings within the ring, excellent results are obtained when isocyanuric acid serves as the nucleus and is substituted with one, two or three alkylhydroxyphenyl groups.

The present alkylhydroxyphenylcarboalkoxy substituted nitrogen heterocycles are useful stabilizers for a wide variety of organic materials. They are extremely effective protective agents for organic polymeric materials, both natural and synthetic, which are subject to the deleterious eflfects of oxygen, heat .and ultraviolet or visible light. They are especially useful as stabilizers for (rolefin polymers and copolymers, acetal polymers, polyamides, polyesters and polyurethanes.

DETAILED DESCRIPTION The compounds of the present invention are alkylhydroxyphenylcarboalkoxy substituted nitrogen heterocycles. More specifically the compounds contain one or more alkylhydroxyphenyl groups bonded through carboalkoxy linkages to nitrogen atoms of a heterocyclic nucleus, said nitrogen atoms located between two carbonyl or thiocarbonyl groups in the ring. The heterocyclic nucleus for the present compounds will therefor contain one or more imidodicarbonyl (iii-l groups or imidodithiocarbonyl (iii) groups. The compounds of the present invention are represented by the general formula 45 r "I E r I E OH i gr omh -oeams ii B (I) wherein n is an integer from 1 to 12, m is an integer from 0 to 8, R is hydrogen or a hydrocarbon radical containing from 1 to 12 carbon atoms, X is oxygen or sulfur and A is a bivalent molecular grouping. The bivalent radical A may be a hydrocarbon radical, such as alkylene or phenylene, or may contain one or more heteroatoms or other functional groups, such as NH, C=S, C=O or the like. In the latter instance where more than one NH group is present in the ring it will be possible to prepare compounds containing a plurality of alkylhydroxyphenyl groups. While R is preferably hydrogen or a hydrocarbon radical, it may be any other group capable of being substituted on an aromatic ring, such as halogen or a nitro group. Compounds of Formula I which are especially useful for the present invention are those wherein X is oxygen, n is an integer from 1 to 8, m is an integer from 1 to 4 and the hydroxyl group is in the 4-position on the ring and is hindered, i.e., has positioned on the ring immediately adjacent thereto at least one alkyl group containing from 1 to 12 carbon atoms.

The nitrogen heterocycle serves as the nucleus for attaching alkylhydroxyphenyl groups of the formula wherein R is the same as defined for formula I. So long as the heterocyclic compound contains one or more nitrogen atoms in the ring with two carbonyl or thiocarbonyl groups immediately adjacent thereto such as iii, iii 0. iii

the heterocyclic compound can be suitably substituted for the purposes of the present invention. Heterocyclic compounds useful for the substitution of one or more alkylhydroxyphenyl groups thereon include uric acid, hydantoin, allantoin, parabanic acid, alloxan, uracil, thymine, barbituric acid, phenobarbitone, isocyanuric acid, succinimide and maleimide and derivatives thereof, phthalimide and derivatives thereof, and similar structurally related materials. With certain heterocyclic compounds such as barbituric acid and isocyanuric acid, for example, where the ring contains more than one nitrogen atom having two carbonyl or thiocarbonyl groups immediately adjacent thereto, it is possible for a plurality of alkylhydroxyphenyl groups to be substituted. For example, two alkylhydroxyphenyl groups could be substituted on the barbituric acid nucleus and in the case of isocyanuric acid up to three alkylhydroxyphenyl groups could be substituted in accordance with the present invention. It is not necessary, however, in the case of barbituric acid 'or isocyanuric acid that all of the nitrogen atoms of the ring be substituted. It Will sufi'ice if only one nitrogen atom be substituted in such a manner, the remaining nitrogen atoms of the ring being substituted with hydrogen or some other radical. A Wide variety of structural modifications are therefor possible with the compounds of the present invention.

A useful class of compounds for use as stabilizers for organic materials, particularly polymeric materials, are the derivatives of isocyanuric acid. These compounds contain one or more alkylhydroxyphenyl groups bonded to the isocyanuric acid nucleus through a carboalkoxy linkage and have the structural formula wherein R is an alkylhydroxyphenylcarboalkoxy group having the formula R R E r *1 OH O -C H wherein n, m and R are the same as defined for formula I above; and R" and R" .are the same as R or are hydrogen, a hydrocarbon radical containing from 1 to 20 carbon atoms such as alkyl, cycloalkyl, aryl, alkaryl or aralkyl, a hydroxyalkyl group containing from 1 to 12 carbon atoms or an alkylcar-boalkoxy group containing from 2 to 20 carbon atoms. Especially useful derivatives of isocyanuric acidare those compounds wherein two, and more preferably all, of the nitrogens of the ring are substituted with radicals of the formula III. Additionally, it has been found that excellent results are obtained 'when the alkylhydroxyphenylcarboalkoxy group has the formula R: I i-a (IV) wherein n is an integer from 1 to 8, m is an integer from 1 to 4, R is an alkyl group containing from 1 to 8 carbon atoms, and R and R are hydrogen or alkyl groups containing from 1 to 8 carbon atoms. More preferably R is a tertiary alkyl group containing from 4 to 8 carbon atoms, R is an alkyl group containing from 1 to 8 carbon atoms and R is "hydrogen. An especially preferred class of compounds of the present invention are those wherein R, R" and R of the formula II are alkylhydroxyphenyl carboalkoxy groups of formula IV wherein n is an integer from 1 to 3, m is an integer from 1 to 3, R and R are tertiary alkyl groups containing from 4 to 8 carbon atoms and R is hydrogen. Excellent results are obtained with 2,2-'2"-tris[3,3,5-di-t-butyl 4 hydroxyphenyl)propionyloxy]ethylisocyanurate, alternatively named as 3,5-di-t-butyl-4-hydroxyhydrocinnamic acid triester with 1,3,5-tris(2-hydroxy-ethyl)-s-triazine-2,4,6- (1g, 35, 5.11) -trione, wherein R, R" and R' of formula II are alkylhydroxyphenylcar-boalkoxy groups of formula IV wherein n is 2, m is 2, R and R are t-butyl groups and R and R are hydrogen.

From the large number of compounds encompassed by the present invention, the following are intended only to be representative:

N -2- 3 (3,5 -di-t-butyl-4-hydroxy-phenyl propionyloxy]- ethylsuccinimide;

N-2- [3 (3,5 -di-,t-butyl-4-hydroxy-phenyl propionyloxy] ethylphthalimide;

2,2,2-tris [3 3,5 -di-t-butyl-4-hydroxyphenyl propionyloxy] ethyltrithioisocyanurate;

2,2,2"-tris [3 (3 ,5 -di-t-butyl-4-hydroxyphenyl) propionyloxy] ethylisoeyanurate;

2,2,2-tris [3 3-methyl-4-hydroxyphenyl)- propionyloxy] ethylisoeyanurate;

2,2',2"-tris [3 (3-t-amyl-4-hydroxyphenyl) propionyloxy] ethylisoeyanurate;

2,2,2"-tris [3 (3 -octyl-4-hydroxyphenyl propionyloxy] ethylisoeyanurate;

2,2',2"-tris 3 3,5 -diisopropyl-4-hydroxyphenyl) propionyloxy] ethylisoeyanurate;

2,2,2-tris 3 (3 ,5 -dimethyl-4-hydroxyphenyl) propionyloxy] ethylisoeyanurate;

2,2',2-tris [3 (3 ,5 -di-t-butyl-4-hydroxyphenyl propionyloxy] methylisocyanurate;

2,2'-bis [3 3,5 -di-t-butyl-4-hydroxphenyl) pro pionyloxy] 1-methylethylisocyanurate;

6,6,6-tris 3 (3 ,5 -di-t-butyl-4-hydroxyphenyl) propionyloxy] hexylisocyanurate;

2- [3 3,5 -di-t-butyl-4-hydroxyphenyl propionyloxy] -2,2-bis (hydroxy ethylisocnayurate;

2,2'-bis [3 3 ,5 -di-t-butyl-4-hydroxyphenyl) propionyloxy] 2- (hydroxy ethylisoeyanurate;

2,2-bis (octadecyloxy -2"- [3 (3 ,5 -di-t-butyl-4-hydroxyphenyl propionyloxy] ethylisocnaurate;

2,2-bis [3 (3 ,5 -di-t-butyl-4-hydroxyphenyl propionyloxy] 2"- (dodecyloxy) ethylisoeyanurate;

2,2',2"-tris 3,S-di-t-butyl-4-hydroxybenzoyloxy) ethylisoeyanurate;

2,2,2"-tris 2-methyl-3- 3,5 -di-t-butyl-4-hydroxyphenyl propionyloxy] ethylisoeyanurate and the like.

The alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycles of the present invention are useful stabilizers for a wide variety of organic materials. They are especially useful to prevent oxidative, thermal and photochemical degradation in polymeric materials, both natural and synthetic. The high degree of effectiveness of the present stabilizer compounds is attributed at least partially to their high molecular weight and excellent compatibility with most organic materials. The present compounds are also advantageous in that they are capable of containing two or three alkylhydroxyphenyl substituents per molecule.

Organic materials stabilized in accordance with the present invention include both natural and synthetic polymeric materials. The following are representative of the polymers which can be eflectively protected by the addition of a stabilizing amount of an alkylhydroxy phenylcarboalkoxy-substituted nitrogen heterocycle thereto: homopolymers of ethylene, propylene, butene-l, isobutylene, pentene-l, hexene-l, 4-methylpentene-1 and the like or copolymers thereof such as ethylenepropylene copolymer, a copolymer of ethylene and butene-l, a copolymer of 4-methyl-1-pentene and hexene-l, and the like; ethylene-propylene terpolymers where the third monomer is a diene such as 1,4-hexadiene, 2-methyl-1,4- hexadiene, a dimethyl-l,4,9-decatriene, dicyclopentadiene, vinylcyclohexene, vinylnorbornene, ethylidenenorbornene, methylenenorbornene, norbornadiene, methylnorbornadiene, methyltetrahydroindene, and the like; polyacetal resins such as homopolymers obtained from the polymerization of formaldehyde and acetal copolymers derived from trioxane; polyesters obtained by the condensation of saturated or unsaturated anhydrides or dibasic acids, such as maleic, fumaric, itaconic or terephthalic anhydrides or fumaric, adipic, azelaic sebacic or isophtbalic acids, with a glycol such as propylene glycol, ethylene glycol, diethylene glycol, neopentyl glycol or trimethylpentane diol; polyurethanes derived from a glycol such as trimethyl propane glycol, butanediol, or a mixture thereof, or a polyol derived from a polyester, polyether or derivative of polycaprolactone, with a polyisocyanate such as an aromatic or aliphatic diisocyanate or isocyanate-terminated prepolymer; and polyamides such as polycaprolactam or those obtained by the condensation of hexamethylenediamine with adipic or sebacic acid or the like. The compounds of this invention are also useful for the stabilization of natural rubber; halogenated rubbers; polymers derived from conjugated dienes such as polybutadiene, copolymers of butadiene and styrene, acrylonitrile, acrylic acid, alkyl acrylates or methacrylates, methylvinyl ketone, vinyl pyridine and the like, polyisoprene or polychloroprene; vinyl polymers such as polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinyl acetate, copolymers of vinyl chloride with vinylidene chloride, butadiene, styrene, vinyl esters, acrylic or methacrylic acid, or other a,fl-olefinically unsaturated acids and esters thereof such as alkyl acrylates and methacrylates, or,B-olefinically unsaturated ketones and aldehydes and the like; homopolymers and copolymers of acrylic monomers such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, 2-ethylhexyl acrylate, acrlamide, methacrylamide, N-methylol acrylamide, acrylonitrile, methacrylonitrile or the like; polycarbonates; epoxy resins such as those obtained by the condensation of epichlorohydrin with bisphenols and copolymers of ethylene oxide or propylene oxide with epichlorohydrin; and like polymeric compositions. In general, any polymeric system subject to degradation as a result of oxidative, thermal or photochemical eifects will be stabilized by the addition of a small amount of the present compounds thereto.

In addition to the above-mentione polymeric organic materials the alkylhydroxyphenylcarboalkoxyeubstituted nitrogen heterocycles are useful to stabilize nonpolymeric organic materials. Waxes, synthetic and petroleumderived lubricating oils and greases, mineral oils, fat, tallow, lard, codliver oil and sperm oil, vegetable oils such as castor, linseed, peanut, palm and cotton seed, fuel oil, diesel oil, gasoline and similar materials are effectively stabilized with the compounds of the present invention.

The compounds of the present invention are especially useful for the stabilization of u-monoolefin homopolymers, copolymers and terpolymers, polyacetal homopolymers and copolymers, polyamides, polyesters and polyurethanes. Both high and low density polyethylene, polypropylene, polyisobutylene and poly4-methyl-pentene-l show markedly improved resistance to oxidative, thermal and photochemical degradation when stabilizing amounts of the present compounds are added thereto. 'Ethylenepropylene copolymers an ethylene-propylene terpolymers,

containing less than about 10% by weight of a third monomer containing multiple unsaturation, are effecitvely stabilized with the alkylhydroxyphenylcarboalkoxysubstituted nitrogen heterocycles. Polymer blends of two or more copolymers or homopolymers derived from amonoolefins are also stabilized in accordance with the present invention.

The amount of stabilizer employed will 'vary with the organic material to be stabilized and the particular alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycle employed. In general, for effective stabilization of most organic materials an amount of alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycle ranging from amout 0.001% to about 10% by weight based on the weight of the organic material will be employed. In most applications the amount of stabilizer will vary between about 0.01% and about 5% by weight. When amonoolefin homopolymers, copolymers or terpolymers are to be stabilized, about 0.05% to about 2.5% by weight of the alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycle based on the weight of the polymer will be used. Although certain of the alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycles will be more useful in some applications than in others, any of the compounds of the present invention employed in an amount as defined above will be an elfective stabilizer for organic materials.

The compounds of this invention are readily incorporated into most organic materials and generally require no special processing. Conventional methods of incorporation have been found to be adequate. For example, the alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycles can be incorporated into the polymers by mixing on a rubber mill or in a Banbury mixer or they may be added alone, in a suitable solvent, or masterbatched with other compounding ingredients to a solution or dispersion of the polymer. The solubility of the present compounds in a wide variety of organic solvents facilitates their use in solution and also renders them compatible with most oils and lubricants.

The present compounds are compatible with conventional compounding ingredients such as processing oils, plasticizers, lubricants, anti-sticking agents, fillers, reinforcing agents, sulfur and other curing agents, accelerators, anti-foaming agents, rust inhibitors and the like. They are also compatible with other known antioxidants, antiozonants, color and heat stabilizers, ultraviolet absorbers and the like, and when employed in combination with many of these a synergistic effect will be obtained.

When the alkylhydroxyphenylcarboal'koxy-substituted nitrogen heterocycles are combined with peroxide decomposing compounds such as dithiocarbamates, zinc dialkylthiophosphates, phosphites such as tris(p-nonylphenyl)phosphite and tridecylphosphite, organic sulfides and similar sulfur-containing compounds, a marked increase'in the stability of the resulting polymer composition over that obtained by employing an identical amount of either stabilizer component individually is obtained.

Peroxide decomposing compounds such as the organic sulfides described in US. Pat. No. 2,519,755 are advantageously employed in conjunction with the novel compounds of this invention to give highly effective synergistic stabilizer compositions. Especially useful organic sulfides are diesters of p-thiodipropionic acid having the formula U R40 C CHaCHr-S-CHmC H20 0 R4 wherein R is a hydrocarbon radical containing from about 6 to 20 carbon atoms such as octyl, nonyl, decyl, lauryl, cetyl, stearyl, palmityl, benzyl, cyclohexyl and the like.

Also useful in combination with the alkylhydroxyphenylcarboalkyl-substituted compounds of the present invention to obtain synergistic activity are thiopropionamides, that is, compounds containing one or more molecular groupings of the formula l 1" N-C-CHCH2SRI wherein R is a hydrogen or a methyl radical and R is a hydrocarbon radical containing from 1 to 24 carbon atoms. Such thiopropionamide compounds include bisand tris-thiopropionamides such as described in copending application Ser. No. 873,650. Illustrative of useful sulfur-containing compounds of the above type which may be used in combination with the alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycles include N,N'-methylene-bis [B- (octylthio) propionamide] N,N'-methylene-bis [fl-(octylthio -u-methylpropionamide] N,N-methylene-bis B- dodecylthio propionamide] N,N'-methylene-bis [13- (hexadecylthio propionamide] N,N'-methylene-bis [fl-octadecylthio -a-methylpropion amide] hexahydro-1,3 ,5 -tris [[3- (octylthio) pro pionyl] -s-triazine,

hexahydro-1,3,5-tris [fl-(octylthio) -a-methylpropionly] s-triazine,

hexahydro- 1,3,5 -tris 13- dodecylthio) propionyl] s-triazine,

hexahydro- 1,3,5 -tris 8- (octadecylthio propionyl] s-triazine,

hexahydro- 1,3 ,5 -tris B- (octadecylthio) -oc-methylpropionyl [-s-triazine,

hexahydro-1,3,5-tris [fi-(phenylthio )propionyl1- s-triazine,

and the like.

Additionally, alkylcarboxyalkylthiopropionamides, that is, sulfur-containing compounds containing one or more groups having the structural formula wherein R is hydrogen or a methyl group, J: is an integer from 1 to 9 and R is a hydrocarbon radical containing from 1 to 24 carbon atoms, may be advantageously employed in combination with the alkylhydroxyphenylcarboalkoxy-substituted compounds of the present invention. Specific alkylcarboxyalkylthiopropionamides which may be employed include N,N-methylene-bis[,3-(n-dodecyl-2-carboxyethy1thio) propionamide] N,N-mehtylene-bis 3- n-dodecyl-Z-carb oxyethylthio methylpropionamide] N,N'-methylene-bis ,3- n-dodecylcarboxymethylthio) -amethylpropionamide] N,N'-methylene-bis [fl- (octadecyl-Z-carboxyethylthio) propionamide] N,N'-methylene-bis [fi- (octadecyl-2-carboxyethylthio -amethylpropionamide] hexahydro-l,3,5-tris [p-(n-dodecyI-Z-carboxyethylthio) propionyl] -s-triazine,

hexahydro-1,3 ,5 -tris fln-dodecylcarboxymethylthio) -amethylpropionyl] -s-triazine,

hexahydro-1,3,5-tris[ 3-(hexadecyI-Z-carboxyethylthio) propionyl] -s-'triazine,

hexahydro-1,3,5-tris 3-(octadecyl-Z-carboxyethylthio propionyl] -s-triazine,

hexahydro- 1,3,5 -tris ,8- (octadecyl-2-carboxyethylthio -amethyl propionyl] -s-triazinc,

and the like.

When combinations of stabilizers are employed to obtain synergistic activity, the total amount of the stabilizer combination will range between about 0.01% and by weight based on the polymer composition. Excellent results have been obtained when the total stabilizer concen- 8 tration is between about 0.1% and 2% by weight and the weight ratio of the sulfur-containing compound to the alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycle is about 1:1. The weight ratio of the two components can be varied between about 5:1 and 1:5 and still obtain synergistic activity.

To obtain the alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycles any number of reaction schemes may be employed. Esterification of a hydroxyalkyl-substituted nitrogen heterocycle with an acid of the formula CmHm C O OH wherein R and m are the same as defined above in formula I, is particularly convenient to prepare the present compounds. The esterification reaction will generally be conducted with an acidic catalyst in an inert solvent. The amounts of reactants employed will be determined by the degree of substitution desired and the particular nitrogen heterocycle to be substituted. For example, if a tris- (hydroxyalkyl)isocyanurate is to be completely substituted, three mols of the acid will be employed per mol of the isocyanuric acid derivative. If partial substitution of the nitrogen heterocycle is desired, the amount of the acid reacted therewith will be decreased proportionately in accordance with the desired degree of substitution.

The acid to be reacted may be obtained by any of the conventional methods including hydrolysis of an ester precursor. Similarly, the hydroxyalkyl-substituted nitrogen heterocycle may be obtained by a variety of methods depending on the particular hydroxyalkyl group to be substituted. For example, hydroxymethyl groups may be substituted on isocyanuric acid or other ntirogen heterocycle by reaction with formaldehyde. Three mols of formaldehyde would be reacted with one mol of cyanuric acid at an elevated temperature to obtain tris(hydroxymethyl) isocyanurate. Tris(2-hydroxyethyl)isocyanurate may be obtained by the reaction of ethylene oxide and cyanuric acid in dimethylformamide or dimethylacetamide. If long chain hydroxyalkyl groups are to be substituted they may be prepared by the procedure described in US. Pat. No. 3,249,607.

The following Examples serve to illustrate the invention more fully. In these Examples all parts and percentages are on a weight basis unless indicated otherwise. Parts of stabilizer are based on parts of polymer. Various terms used throughout the Examples have been abbreviated for convenience and these are as follows:

t-Bu=tertiary butyl sec-Bu=secondary butyl Me=methyl THPI=2,2,2"-tris[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy]ethylisocyanurate EXAMPLE I THPI was prepared by the esterification of 3-(3,5-di-tbutyl-4-hydroxyphenyl)propanoic acid with tris-(Z-hydroxyethyl)isocyanurate. The 3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoic acid was obtained by first preparing the corresponding methyl ester and then hydrolyzing the ester to the acid. To obtain the methyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoate, 66.2 grams (0.32 mol) 2,6-di-tbutylphenol was reacted with 3.16 grams sodium methoxide in 250 mls. N,N-dimethylformamide which was previously dried by passing over 3 A. molecular sieves. The reactor and its contents were then heated for approximately one hour at a maximum temperature of about C. to take olf the methanol. The reaction mixture was allowed to cool to about 35 C. and 25.1 grams (0.29 mol) methylacrylate charged. The reaction was heated for about 6 hours at reflux and then neutralized by the addition of hydrochloric acid (1:1 by volume). The N,N-dimethylformamide was removed by stripping under reduced pressure and about 90% yield of crude methyl-3-(3,5-di-tbutyl-4-hydroxyphenyl)propanoate based on the amount of acrylate charged was obtained. The crude reaction product was vacuum distilled at 180 C. and 0.3 mm. mercury to obtain pure methyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoate melting at 62-63 C.

Methyl-3-(3,5-di-t-butyl 4 hydroxyphenyl)propanoate obtained from several runs as described above was hydrolyzed to obtain the acid by dissolving about 920 grams methyl-3- (3 ,5-di-t-butyl-4-hydroxyphenyl propanoate in about kilograms of water containing about 460 mls. methanol and 175 grams sodium hydroxide. The reaction mixture was refluxed for about one hour, the pH adjusted to about 8 by the addition of 1:1 hydrochloric acid and 26.2 grams sodium hydrosulfite added. The reaction mixture was refluxed until it was essentially colorless. 1:1 Hydrochloric acid was then added to reduce the pH to about 2 and precipitate the product. The resulting 3 (3,5 di-t'butyl-4-hydroxyphenyl)propanoic acid was washed and dried in a vacuum oven at 50 C. A 97% yield of the 3-(3,S-di-t-butyl-4-hydroxyphenyl)propanoic acid (M.P. 173-174" C.) was obtained.

Esterification of the 3-(3,5-di-t-butyl-4-hydroxyphenyl) propanoic acid with tris-(2-hydroxyethyl)isocyanurate, obtained by the reaction of cyanuric acid with ethylene oxide in N,N-dimethylformamide as described by R. W.

.Cummins, Amer. Chem. Soc, 28, 85 (1963), gives THPI in good yield. The reaction was conducted in a 12 liter glass reactor equipped with a Dean-Stark water trap 10 troscopy and nuclear magnetic resonance spectroscopy.

Results of elemental analysis of the product are as follows:

CloHuNsOn Percent Theory Found Carbon 69. 16 69. 18 Hydrogen 8. 36 8. 62 Nitrogen 4. 03 3. 96 Oxygen 18. 44 18. 24

Compounds set forth in Table: I were identified by infrared spectroscopy, nuclear magnetic resonance spectroscopy and/ or elemental analysis.

TABLE I Compound 2: y A B R" 3'" Formula 2 t-Bu t-Bu R R CuHnNaOu 2 t-Bu t-Bu. R R CuHnaNlOn 2 t-Bu t-Bu R R CnHmNaOu 2 t-Bu t-Bu -CH:CH2OH CH2CH2OH CrcHavNzOl 2 t-Bll t-Bll R CH:CH7OH cnHnNlom 2 t-Bu t-Bu u (I) CnHmNxOm -C 2CH2 C( :)mCHa -CH:CHzOC(CH1)i|CH| I(g) 2 2 t-Bu t-Bu R (H) CuHlsNlOu -CH;CH;OC(CH2)10CH;

2 0 t-Bu t-Bu R R CMHHNIOH 2 3 t-Bu t-Bu R R Cu uNsOi: 2 2 Me Me R R CnHsiNsOi: 2 2 Me t-Bu R R ChflevNa u 2 2 t-Bu H R R cts uzNaou 2 2 sec-B11 sec-Bu R R ConHuNaOn by combining 157 grams (0.6 mol) tris(Z-hydroxyethyl) EXAMPLE II isocyanurate and 552 grams (1.98 mols; 10% molar excess) 3-(3,5-di-t-butyl-4-hydroxyphenyl)propanoic acid in three liters dry xylene. Hydrogen chloride was then bubbled into the reaction mixture until it was saturated and 5.53 grams p-toluene sulfonic acid charged. The reaction mixture was then heated to reflux for about 6 hours during which time about 33 mls. water was removed by azeotropic distillation, allowed to cool and the catalyst residues removed by filtration. The xylene was removed under reduced pressure to obtain a glass-like crude product. This crude product was dissolved in about 2 liters of diethyl ether and washed with several portions of 0.5% aqueous sodium hydroxide until the wash had a pH of 10 or greater and then with water. After drying the ether was stripped under vacuum and about 95% yield THPI obtained as a crude glassy material having a softening point of about 67 C. This material was further purified by dissolving at 65-70 C. in about 5 liters heptane and allowing the solution to cool to room temperature with vigorous agitation.

By recrystallization from isopropanol THPI is obtained as a colorless crystalline material melting at 127 C.l28 C. The product was identified as T HPI by infrared spec- Employing a procedure similar to that described in Example I, analogous trithioisocyanurates were prepared by reacting three mols 3-(3,S-di-t-butyl-4-hydroxyphenyl) propanoic acid with one mole of the hydroxyethyl-substituted thioisocyanurate compound obtained by the reaction of trithiocyanuric acid with a molar excess of ethylene oxide in N,N-dimethylformamide at about C.

EXAMPLE III 11 (3,5 -di t-butyl-4-hydroxyphenyl)propionyloxy]ethylphthalimide is 71.80% carbon, 7.37% hydrogen, 3.11% nitrogen and 17.72% oxygen.

EXAMPLE IV spectroscopy and elemental analysis, the results of which were as follows:

Cza aaNOs Percent Theory Found Carbon 68. 49 6B. 93 Hydrogen. 8. 49 8. 48 Nitrogern. 3. 47 3. 42 Oxygen 19. 85 19. 17

The crystalline material melted at 93.5 C.

EXAMPLE V To demonstrate the utility of the THPI as a stabilizer for a-olefin polymers, 100 parts high density polyethylene was stabilized with 0.05 part THPI and compared against an unstabilized control by measuring the oxidation by differential thermal analysis.

The oxidative stability of the various polymers was measured employing a differential thermal analytical technique such as described by A. Rudin et al. Ind. & Eng. Chem, 53, No. 2, 137-140 (1961). This is a quick and convenient method for determining the oxidation resistance of polymers. Stabilizers were incorporated into the polymer samples to be tested by preparing a standard solution of the stabilizer in benzene, adding the proper volume of the standard solution to a known weight of the polymer so as to give the desired stabilizer level, and evaporating the benzene by air drying. Two milligram samples are run in air and in nitrogen with the instrument programmed to give a temperature rise of C./ minute. From the resulting thermogram the oxidation exotherm can be observed. The higher the temperature at which the oxidation exotherm appears the greater the oxidative resistance of the sample.

The unstabilized polyethylene sample had its oxidation exotherm at 200 C. whereas the oxidation endotherm for the sample stabilized with 0.05 part THPI appeared at 223 C.

To further demonstrate the effectiveness of the THPI, it was compared with a well-known commercially available stabilizer material, Irganox 1010. Irganox 1010 is sold by Geigy Chemical Corporation and is tetra [methylene 3 (3,5 di-t-butyl-4-hydroxyphenyl)propionate] methane. High-density polyethylene stabilized with 0.05 part Irganox 1010 showed an oxidation exotherm at 220 C.

EXAMPLE VI Polypropylene stabilized with 0.25 part THPI and tested in accordance with the procedure described above in Example V had an oxidation exotherm of 227 C. Unstabilized polypropylene had its oxidation exotherm of 176 C.

Polypropylene samples stabilized with THPI were also subjected to long-term oven aging to demonstrate the efiectiveness of the stabilizer compounds of the present invention by themselves and in combination with sulfurcontaining synergistic compounds such as distearylthiodipropionate. To prepare the test samples polypropylene was dry blended with the stabilizers and then fluxed in an extruder at 450 F. The extrudate was pelletized and hot pressed at 420 F. into 10 mil thick specimens which were aged in an air-circulating oven at 150 C. The

Sample a b c d e I Polypropylene 100 100 100 100 100 PI 0. 1O 0. 25 0. 10 0. 25 Distearylthiodipropionate- 0. 25 0. 25 0. 25 Days to failure 1 20 45 45 59 +1 EXAMPLE VII Ethylene-propylene terpolymer (53% ethylene, 43% propylene and about 4% ethylidene norbornene) was stabilized with 0.3 part THPI and two other commercially available stabilizer compositions at the 0.3 part level. Test samples were prepared by forming a 20% cement by dissolving the terpolymer and stabilizer in xylene and then casting a film of the desired thickness on an infrared salt (KBr) plate by evaporation of the solvent. The specimens were aged in an air-circulating oven at C. and removed at regular intervals to measure the development of the carbonyl content by infrared analysis. The carbonyl content is plotted versus aging time and failure of the sample is marked by a sharp break in the curve. Test results were as follows:

Stabilizer: Hours to failure None 1 THPI 22.8 n Octadecyl s -(3,5 di-t-butyl-4-hydroxyphenyl)propionate Tetra[methylene 3 (3,5-di-t-butyl-4-hydroxyphenyl)propionateJmethane 16.8

The superior oxidative resistance of the samples stabilized with THPI is evident from the above data.

EXAMPLE VIII One part THPI was incorporated in a synthetic natural rubber composition (cis-polyisoprene) and the stabilized rubber tested in a Brabender Plasticorder to measure the stability of the polymer. The stabilized polymer was placed in the heating chamber, heated at C. and the torque recorded. The time required for the torque to drop 1000 units from the maximum (2500 units) was 7.5 minutes for the stabilized sample. An unstabilized control ran for only 3 minutes.

EXAMPLE IX A polymer blend of polyvinyl chloride, acrylonitrilebutadiene-styrene terpolymer and butadiene-nitrile polymer was stabilized by the addition of 4 parts THPI and the polymer tested in accordance with ASTM D-l925- '63T for the development of the yellowness during milling at 350 F. Initially both the unstabilized polymer blend and the stabilized polymer blend has a yellowness factor of 41. After 90 minutes milling the unstabilized blend deteriorated to an 82 yellowness factor while the stabilized composition only had a yellowness factor of 67.

EXAMPLE X Acrylonitrile-butadiene-styrene latex was coagulated and 1.75 parts THPI added to the dry resin in a blender. The resulting stabilized composition was tested employing the differential thermal analytical technique previously described. A 50% oxygen atmosphere was used. The stabilized acrylonitrile-butadiene-styrene composition showed no oxidation exotherm until about 300 C. The unstabilized composition had an oxidation exotherm at 180 C.

EXAMPLE XI THPI was evaluated as an oxidation inhibitor in the ASTM D-943 turbine-oil oxidation test and compared against an unstabilized sample. The turbine-oil was Texaco Regal Oil A, a HVI neutral turbine oil. 2.5% THPI plus 0.05% of a rust inhibitor, tetrapropenylsuccinic anhydride, were added to the oil. The stabilized turbine oil had a life of 525 hours whereas the unstabilized oil deteriorated within 24 hours.

EXAMPLE XII A polyether-based urethane was stabilized with 0.5% THPI by adding the THPI to the polyol blend prior to heating to the reaction temperature. The stabilized poly-' EXAMPLE XIII A plasticized high temperature polyvinyl chloride resin suitable for wire and cable applications was stabilized by the addition of THPI and Bisphenol A. The resin and stabilizer were mixed in a laboratory Banbury at a temperature of 345 to 360 F. and then milled at 310 F. for about minutes. Specimens were die-cut from 0.035 and 0.075 sheets and pressed for 5 minutes at 345 F. between ferro-type plates with approximately 1400 p.s.i. being applied on the platens. The samples were ovenaged at-158" C. for 7 days and the physical properties determined. Percent retention of elongation for the samples after aging was as follows:

EXAMPLE XIV Two acrylic ester latices were stabilized by the addition of 0.5 part THPI. Acrylic latex A contained about 95 parts ethyl acrylate and 3 parts acrylonitrile with acrylic acid and N-methylol acrylamide interpolymerized. Latex B contained a mixture of ethyl acrylate and n-butyl acrylate (85 parts) polymerized with 10 parts acrylo-" nitrile and acrylamide. THPI was added to the latices as a 20% emulsion. The resulting stabilized latices were then diluted to"% total solids and used to saturate 10 mil bleached Kraft flat paper (Patterson Code 515) by immersing the paper in the latex for seconds, dripdrying and curing for 10 minutes. The papers were heataged at 300 F. in an air-circulating oven and the percent reflectance, which is a measure of the discoloration of the paper, measured at hour intervals. Initial reflectance readings before aging for both the stabilized and unstabilized saturated papers ranged between 77% and 78.5%. After hours heat-aging the reflectance for the unstabilized paper saturated with Latex A was 27.5% as compared with 44.5% for the stabilized paper. For the papers saturated with Latex B, the reflectance for the paper coated with the unstabilized latex dropped to 40.5% after 25 hours aging whereas the reflectance for the paper saturated with the stabilized latex was 59.9%.

EXAMPLE XV A styrene-butadiene latex was stabilized by the addition of THPI to the latex (1.25 parts based on dry polymer). After coagulation, the crumbs were milled and 2" x 6" samples cut from the sheet for oven aging at 105 C. Mooney viscosity data (ML 4-212 F.) indicated that marked improvement of the stability of the SBR samples stabilized with the THPI over that of the unstabilized SBR. Similarly, marked superiority of the stability of THPI stabilized SBR was observed over SBR stabilized with 1.25 parts Antioxidant 2246, 2,2'-methylenebis-4-methyl-6-t-butylphenol sold by American Cyanamid Company. Similar improved stability was observed for butadiene-acrylonitrile copolymer stabilized with THPI at a 2.5 parts level.

14 EXAMPLE XVI parts of polyvinyl chloride (Geon 101E? having a density of 1.38) plasticized with about 50 parts dioctyl phthalate and containing 3 parts stearic acid was oven aged at 325 F. The color tone of the specimens was ob served at 10-minute intervals. A marked improvement in the resistance to discoloration was observed for the samples stabilized with the THPI as compared with unstabilized PVC samples.

EXAMPLE XVII A natural rubber white stock was prepared in accordance with the following recipe:

Ingredient: Parts Natural rubber 100 Stearic acid 2 Zinc oxide 5 Titanium dioxide 50 Sulfur 2.75 Benzothiazyl disulfide 1 Tetramethylthiuram disulfide 0.1 THPI 1 A copolymer of ethylene oxide and epichlorohydrin was compounded in a conventional recipe with zinc stearate, red lead and carbon black and stabilized with 1 part THPI. The cured (30 minutes at 347 F.) composition was then air aged in a test tube for 168 hours at C. The stabilized composition showed a tensile loss of only 79% and a hardness loss of only 21 points after aging. The unstabilized copolymer composition failed completely under these same test conditions.

EXAMPLE XIX Other compositions stabilized with varying amounts of THPI are as follows:

Material: Parts of THPI Polystyrene 0.5 Neoprene sponge 1.0 Nylon 6 0.5 Cyclohexene 0.001 Mineral oil 0.1 Polyoxymethylene 0.5 Polyethylene terephthalate resin 0.5

All of these compositions showed improved oxidative stability over the unstabilized controls.

EXAMPLE XX Unstabilized acetal copolymer resin obtained by polymerizing formaldehyde and ethylene oxide was tested for oxidative stability employing the differential thermal technique previously described. Three levels of THPI were employed. Since the acetal copolymer deteriorates in two stages, first oxidizing and then depolyrnerizing, both were considered. Results were as follows:

Depolymerization endotherm Oxidation exoth Parts stabilizer 1 5 EXAMPLE XXI A series of stabilized polypropylene compositions were prepared and tested using the differential thermal analytical oxidation test method. All stabilizers were employed at a 0.25 parts level. The 'various stabilizer compounds are identified by reference to the particular Example in which they were prepared. An unstabilized control and sample stabilized with a widely known commercial stabilizer composition were also included in the test. Test results are tabulated below.

Oxidation Exotherm Compound: ControlNone 176 216 I(b) 223 (6) 190 I(d) 217 He) 214 19o I(g) 237 I(h) 197 I(i) 215 1(5) 230 I(k) 233 1 1 215 I(m) 200 II 214 III 212 IV 212 CAO-1* 205 GAO-1 is '4-methyl-2,6-dl-t-butylpheno1 cold by Hooker Chemical Corporation.

EXAMPLE XXII Polyacetal resin as described in Example XX was stabilized with 0.5 parts N-2-[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy]ethylphthalimide and 0.5 parts N- 2 [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy] ethylsuccinimide as prepared in Examples III and IV. Oxidation resistance of the stabilized samples was markedly improved over that of the unstabilized control. Oxidation exotherms for the stabilized samples were absent in both cases while endothermic depolymerization did not occur until 225 C. and 235 C., respectively.

It is evident from the above Examples that the THPI and other alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycles of the present invention are effective stabilizer compounds for a wide variety of organic materials. By incorporating small amounts of the present stabilizer into polymeric materials marked improvements in the oxidative stability of the polymers has been obtained.

We claim:

1. An alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocyclic consisting of phthalimide substituted at the nitrogen atom with an alkylhydroxyphenylcarboalkoxy group having the formula wherein n is an integer from 1 to 8, m" is an integer from 1 to 4, R is an alkyl group containing from 1 to 8 carbon atoms and R and R are hydrogen or an alkyl group containing from 1 to 8 carbon atoms.

2. The alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycle of claim 1 wherein R is a tertiary alkyl group containing from 4 to 8 carbon atoms, R: is an alkyl group containing from 1 to 8 carbon atoms and R is hydrogen.

3. The alkylhydroxyphenylcarboalkoxy-substituted nitrogen heterocycle of claim 2 wherein R is a tertiary alkyl group containing from 4 to 8 carbon atoms and n and m' are integers from 1 to 3.

4. An a1kylhydroxyphenylcarboalkoxy-su'bstituted nitrogen heterocycle of claim 3, N-2-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethylphthalimide.

References Cited UNITED STATES PATENTS 3,161,652 12/1964 Takamatsu et a]. 260-309.5 3,271,402 9/1966 Fahrni et a1. 2 -260 3,306,908 2/1967 Le Suer 260-3263 JOSEPH A. NARCAVAGE, Primary Examiner 

